The new generation of electronic products tends to be light and small, and high-frequency transmission capability is needed, and therefore the wiring density of the circuit board is becoming higher, and the material selection of the circuit board is becoming more demanding. In general, a high-frequency electronic device is bonded to a circuit board. To maintain the transmission rate and the transmission signal integrity, lower dielectric constant and dielectric loss (or dissipation factor) are needed for the substrate material of the circuit board because the signal transmission speed of the substrate and the square root of the dielectric constant of the substrate material are inversely proportional, and therefore a smaller dielectric constant of the substrate material is usually better; moreover, since a smaller dielectric loss indicates smaller loss in signal transmission, the transmission quality provided by a material having smaller dielectric loss is also better.
In general, the substrate of a circuit board is formed by bonding a metal foil and a hydrocarbon resin layer via a lamination method to improve the high dielectric constant and the dielectric loss value, and to increase flame retardance and moisture absorption. The adhesion between the metal foil and the hydrocarbon resin layer affects the properties of the resulting circuit board, and therefore also affects the function and the reliability of the electronic product. However, the adhesion between current hydrocarbon resin material having good dielectric properties and the metal foil is insufficient, such that the function and the reliability of the electronic product made thereby are affected.
Therefore, the development of a substrate having low dielectric constant and low dielectric loss is important topic in the relevant art at this stage. The application of this substrate in the manufacture of a high frequency circuit board is also important topic in the relevant art at this stage.